Aircraft wings and other airfoils are shaped to provide a reaction force as they are moved through the air. In the case of a wing, the desired reaction force is lift. The shape of an airfoil is a primary factor that determines aerodynamic characteristics of the airfoil. One measure of the performance of an airfoil is the ratio of lift to drag. Ideally an airfoil has a high ratio of lift to drag.
A wide variety of airfoil shapes are known. Selecting an airfoil shape involves trading off various airfoil characteristics. For example, there are tradeoffs between lift, drag, and stall characteristics. An airplane wing may have a cross sectional shape that varies along the length of the wing. For example, A wing of an airplane may have one airfoil shape at its root and another airfoil shape at its tip.
Various identification schemes are used to identify airfoil shapes. The National Advisory Committee for Aeronautics (NACA) has developed one orderly system of identifying airfoils. The NACA system includes several families of airfoils. One such family NACA developed is the five digit series. Airfoils in this series are identified by five-digit numbers. The first digit has a value that is ⅔ of the design lift coefficient (in tenths). The second and third digits form a two-digit number having a value that is twice the position of the maximum camber in tenths of chord. The final two digits indicate the maximum thickness in percentage of chord.
One group of airfoils within the NACA five-digit series of airfoils are the 23000-series airfoils. These airfoils have a design lift coefficient of 0.3 and a position of maximum camber at 0.15 of the chord length. The airfoils in the series differ in thickness. NACA 23000-series airfoils tend to offer relatively high lift combined with relatively low drag at cruising speeds. NACA 23000 series airfoils are used on a range of aircraft, including but not limited to the CESSNA™ CARAVAN™ 208 aircraft (which has a wing that at its root has a NACA 23017.424 airfoil and at its tip has a NACA 23012 airfoil) and the BEACHCRAFT™ KING AIR™ aircraft (which has a NACA 23018 airfoil at the root of the wings, blending to a NACA 23012 airfoil at the wing tips).
While the characteristics or profile of NACA 23000-series airfoils are generally satisfactory, there are some significant shortcomings associated with NACA 23000 series airfoils. For example:                NACA 23000-series airfoils can suffer from reduced lift in hot climates;        NACA 23000-series airfoils can suffer from reduced lift under icing conditions, even with protector systems on. Under icing conditions, NACA 23000-series airfoils have been known to exhibit leading edge stall.        
Manufacturers design aircraft to have performance characteristics acceptable for a range of applications. For a specific application, the aerodynamic performance of a particular aircraft may not be ideal. For example, for some applications it might be desirable to have increased lift even if this comes at the expense of increased drag.
Canadian Patent No. 2,054,807 to Barron entitled WING MODIFICATION METHOD AND APPARATUS describes a modification kit for the DeHavilland DH-2 Beaver and the DH-3 Otter aircraft. The modification kit provides a replacement leading edge for the wing together with replacement droop wing tips and wing fence. Holes are drilled into the leading edge of the wing to mount the replacement leading edge on the wing. Thus, attaching the replacement leading edge damages the internal structure of the wing such that the aircraft cannot be returned to its original configuration without significant repair work.
The inventor has recognized various needs that are currently not satisfied including needs for:                ways to reversibly modify the aerodynamic characteristics of airplane wings or other aerodynamic structures.        improved airfoil designs that provide high ratios of lift to drag.        ways to improve aerodynamic characteristics of airplanes having wings incorporating NACA 23000-series airfoils.        ways to provide increased lift in CESSNA CARAVAN and BEACHCRAFT KING AIR aircraft.        